PHYS 0175 Lecture 2 Outline of Last Lecture II. The origins of electric chargea. amberIII. Electricity Outline of Current Lecture IV. Electric Charge and the structure of matterV. Conductors and InsulatorsVI. Principles of chargeVII. Methods of Charginga. Contactb. Induction VIII. Forces between chargesa. Coulomb’s LawIX. Electric Force vs Gravitational ForceCurrent LectureX. Electric Charge and the structure of mattera. the atom consists of the proton, neutron, and electronb. the proton and neutron are located at the nucleus of the atom and make up most of the atom’s weightc. the electrons revolve around the nucleus(negatively charged)d. when an electron is removed from the atom, it has a +1 chargee. when an electron is added to the atom, it has a -1 chargef. the electric charge, whether positive or negative, of 1 Coulomb=charge of6.24*10^18 protons or electronsi. 1 Coulomb=electric current=1Amphere(A)*second(s)XI. Conductors and Insulatorsa. Conductorsi. Charges can move easily around1.Silver, gold, copper,other metals, water,b. Insulators i. Charges cannot move around easily1. Plastic, wood, glass, pure water(no charged ions)c. Semiconductorsi. Allow charge to flow only under certain conditions1. Silicon, germaniumd. Superconductors i. Conducts electricity with 100% efficiency, XII. Principles of chargea. Conservation of chargei. The sum of all electric charges in any closed system is always constant1. If not a closed system, such as in contact with the earth, then the charge will either be lost/gained to neutralize the systema. The earth is a large conductorb. Quantization of chargei. All detectible amounts of charge are whole number multiples of the charge of the proton(e) or electron(-e)XIII. Methods of Charginga. Charging by inductioni. No contact involvedii. Charged item can be brought close to a neutral item1. Cannot create a charge for the neutral item since there is no contact, only can cause a positive and negative end2. The neutral item will distribute its charge, the same sign away from the charged item and the opposite sign near the charged itemiii. Objects must be conductors1. If the object is an insulator and charge cannot move, there will be no charge separation on a neutral item at allb. Charging by contacti. If two objects are of the same size and material and put into contact, then their final charge will be half the sum of their two initial chargesXIV.Forces between chargesa. Coulomb’s Lawb. Newton’s third lawi. Electrostatic force on one object is equal in magnitude and opposite that of the other objectc. F=(k*q1q2)/r^2i. r is the distance between the chargesii. K=9.00*10^9Nm^2/C^2d. The direction of the force vector is:i. Repulsive if charges are alikeii. Attractive if charges are oppositeXV. Electric Force vs Gravitational Forcea. Both the electrical force and the gravitational forces vary inversely with distanceb. However, gravitational force is always attractionc. Electrostatic force can be either attractive or repulsived. Electrostatic force is much stronger than the gravitational
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